lm25085 don't work at Vin 24V

Hi,

Do you have a hardware built with this schematic. I don't see the input bypass capacitor in the schematic.

Hi,

I do not think that the input capacitance is responsible for the fall of the 3.3V over 18V input, however, attached the schematic that I used, it seems that you turn off a power somewhere, even if the wine can be up to 42V.

Andrea

Hi Andrea,

Thank you for verifying the CIN caps. I don't see any ripple network or esr in series with the output capacitor.

Also is the 7V circuit working properly?

Part of 7v works the other does not.
I did try to put the same components of the switching to 3.3V on what to 7v and over 18V up to 32V works, while the other above the 18V not from the most 3.3V.
even with the same load.
I have noticed however, that the pgate is always driven in both switching even above 18V.
I attach the pdf of the master to understand the mistake.
Andrea Penna

Solved the problem by changing the circuit with the wire in photo attached..

It must not be absolutely a short trace between the Vin connected to the capacity for the Vcc with shunt resistance, above the 18V input switching does not work. The change cut the short runway and brought the Vin separately to the shunt resistor with a wire.
To be careful with the master with this component, not reported on the data sheet, so it's misleading schematic recommended.

Regards

Andrea Penna